The value of industrial robots has historically been driven by the automotive industry. However, that value is now being realized in other industries, as robots are being designed for tasks as diverse as cleaning sewers, detecting bombs, and performing intricate surgery. The number of industrial robots sold globally in 2013 was nearly 180,000 units, essentially tripling the number of units sold in 2009, with the automotive, metal, and electronics industries driving the growth.
Prior approaches to calibrating industrial robots use measuring devices either determine the inaccuracies of the robots after the robot is built, or measure work piece positions relative to the robots' positions prior to off-line programming.
Some of the prior art includes:                U.S. Pat. No. 8,651,858 (Berckmans, et al.) discloses a method of creating a 3-D anatomic digital model for determining a desired location for placing at least one dental implant in a patient's mouth. One such method uses a calibration device that involves two intersecting lasers to place a dental implant into a cast model of a patient's mouth. The lasers are not mounted onto a fixture since the fixture-to-robot location is known. The method creates a 3-D anatomic digital model for determining a desired location for placing at least one dental implant in the mouth of a patient.        U.S. Pat. No. 7,979,159 (Fixell) discloses a method and a system for determining the relation between a local coordinate system located in the working range of an industrial robot and a robot coordinate system. The method includes attaching a first calibration object in a fixed relation to the robot and determining the position of the first calibration object in relation to the robot. Then, locating at least three second calibration objects in the working range of the robot, a reference position for each of the second calibration objects in the local coordinate system can be determined by moving the robot until the first calibration object is in mechanical contact with each second calibration object. By reading the position of the robot when the calibration objects are in mechanical contact the relation between the local coordinate system and the robot coordinate system can be calculated.        U.S. Pat. No. 7,945,349 (Svensson, et al.) discloses an invention which relates to a method and a system for facilitating calibration of a robot cell. One or more objects and an industrial robot perform work in connection to the objects, wherein the robot cell is programmed by means of an off-line programming tool including a graphical component for generating 2D or 3D graphics based on graphical models of the objects. The system comprises a computer unit located at the off-line programming site and configured to store a sequence of calibration points for each of the objects, and to generate a sequence of images including graphical representations of the objects to be calibrated and the calibration points in relation to the objects, and to transfer the images to the robot, and that the robot is configured to display the sequence of images to a robot operator during calibration of the robot cell so that for each calibration point a view including the present calibration point and the object to be calibrated are displayed for the robot operator.        U.S. Pat. No. 7,756,608 (Brogardh) discloses a method for calibrating an industrial robot including a plurality of movable links and a plurality of actuators effecting movement of the links and thereby the robot. The method includes mounting a measuring tip on or in the vicinity of the robot, moving the robot such that the measuring tip is in contact with a plurality of measuring points on the surface of at least one geometrical structure on or in the vicinity of the robot, reading and storing the positions of the actuators for each measuring point, and estimating a plurality of kinematic parameters for the robot based on a geometrical model of the geometrical structure, a kinematic model of the robot, and the stored positions of the actuators for the measuring points.        
What is needed is a robot calibration system for use with industrial robots to improve cost and time factors in applications where absolutely accurate robots are not really necessary. Examples include body-in-white applications, resistance welding, material handling, and MIG welding.
Also, what is needed is a robot calibration system that covers a larger surface area, thereby providing improved accuracy for the user.
The primary objective of the robot calibration system of the present invention is to provide a calibration system that is simpler to operate, results in improved precision, involves a lower investment cost, and entails lower operating costs in a manufacturing environment.